1. Technical Field
The present invention relates to a piezoelectric element, a piezoelectric actuator, a liquid ejecting head, and a liquid ejecting apparatus.
2. Related Art
Piezoelectric elements have a structure in which a piezoelectric material composed of a crystallized piezoelectric ceramic or the like is interposed between two electrodes. Therefore, the piezoelectric elements can exhibit deformations such as expansion and contraction or the like by applying an electric field to the piezoelectric material. The piezoelectric elements are used as piezoelectric actuators of liquid ejecting heads and the like. A typical example of the piezoelectric actuators used for liquid ejecting heads is one driven in a flexural vibration mode.
An example of the liquid ejecting heads is an ink jet recording head or the like including a vibrating plate which constitutes a portion of a pressure-generating chamber communicated with a nozzle orifice which ejects ink droplets so that the vibrating plate is deformed by a piezoelectric element to apply pressure to ink introduced into the pressure-generating chamber, ejecting ink droplets from the nozzle orifice. The piezoelectric actuator provided on the ink jet recording head is formed by, for example, forming a uniform piezoelectric material layer over the entire surface of the vibrating plate and cutting the piezoelectric material layer in a shape corresponding to the pressure-generating chamber by lithography so that the actuator can be driven independently for each pressure-generating chamber.
In addition, the piezoelectric layers of such piezoelectric elements are formed by depositing thin films of a piezoelectric material such as lead zirconate titanate (PZT) or the like using a liquid phase process. For example, Japanese Unexamined Patent Application Publication No. 2002-314163 discloses a method for forming films by applying a piezoelectric material multiple times to form a piezoelectric layer. This publication describes that this film forming method can stably form a piezoelectric layer (engineered domain) with preferential orientation of (100) crystal plane in a direction normal to a substrate surface.
However, the performance required for piezoelectric elements becomes more strict, and it becomes difficult to achieve sufficient performance only by applying a piezoelectric material multiple times to form a piezoelectric layer. Therefore, for example, lattice matching between an electrode material and a piezoelectric layer, further lamination of another material (e.g., titanium), and the like are being investigated.
The inventors have found that in order to form a better engineered domain structure, it is important to suppress deterioration of crystals of a piezoelectric material near an interface between a piezoelectric layer and an electrode. It has been also found that the composition of the piezoelectric material greatly affects the control of crystals of the piezoelectric material near an interface between the piezoelectric layer and electrodes which hold the piezoelectric layer therebetween.